This application claims the benefit of co-pending German Patent Application No. 101 02 910.1-42 entitled xe2x80x9cKraftfahrzeug, insbesondere Cabrio, mit aktiv angesteuerten Torsionsstabilisatorenxe2x80x9d, filed on Jan. 23, 2001.
The present invention generally relates to a motor vehicle. More particularly, the present invention relates to a convertible including at least one torsion stabilizer unit being actively controlled to change its length to counteract vibration of the body of the convertible.
It is known in the art that a variety of motor vehicles, especially convertibles, have a body which is not stiff against torsion. Consequently, torsion vibrations of the body of the motor vehicle quickly occur due to an excitation caused by rough, bumpy, or uneven pavements or roads. In case of convertibles, reduced torsion strength is caused by the fact that the stiffness of the body of the convertible is reduced due to the missing fixed top compared to sedans and the like. In convertibles, there also are significant bending vibrations about a transverse axis of the motor vehicle being located in the region of the openings of the doors. The torsion vibrations occur about the longitudinal axis of the motor vehicle corresponding to the direction of motion of the vehicle.
A motor vehicle is known from European Patent Application No. 0 955 228 A2. The known motor vehicle, especially a convertible, includes a body to which struts extending in a longitudinal direction are associated as torsion stabilizers. In another embodiment, two of the struts are designed to be variable in length. Watching units for determining a longitudinal load, control elements for effecting an opposing counterforce, and a control unit for controlling the control elements are associated with the struts. The control elements in the only constructive embodiment are designed as piezo elements which may also be described as potential/pressure converters. In each case, the torsion stabilizers being variable in length as known from European Patent Application No. 0 955 228 A2 are designed and arranged to absorb compressive stresses. In practical operation, it has been found that piezo elements are only capable of effecting the necessary variation in length of the struts to substantially stabilize the body of a motor vehicle at great expense. For this purpose, very high electrical potential has to be used at the piezo elements. In this way, torsion in a dynamic regionxe2x80x94meaning torsion vibrationsxe2x80x94of the respective motor vehicle may be substantially suppressed. However, static torsion of the motor vehiclexe2x80x94for example due to a rough surface on which the motor vehicle is supportedxe2x80x94cannot be prevented. Such static torsion results in deformation of the openings of the doors, for example. Consequently, there are problems during opening and closing the doors of the convertible.
A hose actuator is known from British Patent No. 1 331 756. The hose actuator expands its diameter when hydraulic medium flows into its interior. Consequently, the length of the hose actuator between its connecting locations or supporting locations is shortened. The increase in diameter mainly occurs in the middle region between the connecting locations of the hose actuator. The pressure prevailing in the interior of the actuator is transformed into an increase in diameter and into a simultaneous decrease of length being achieved by expansion-prove supports in combination with an elastic wall of the hose actuator.
Further developments concerning the hose actuator known from British Patent No. 1 331 756 are disclosed in the following patent documents: EP 0 146 261 B1, EP 0 161 750 B1, WO 00/61951, WO 00/61952, DE 195 31 097 C2, and DE 199 17 483 A1. The known applications of known hose actuators are in the quasi-static region, meaning the low frequency region.
The present invention relates to a motor vehicle including at least one torsion stabilizer unit having a length and including at least one hydraulic actuator unit. The motor vehicle further includes at least one control unit being designed and arranged to actively control the length of the at least one torsion stabilizer unit. More particularly, the present invention relates to a convertible.
The present invention also relates to a motor vehicle the body of which includes a plurality of doors, a plurality of openings for the doors, at least one sill plate being located in the region of one of said openings of the doors and supporting sheet metal. At least one hydraulic medium supply circuit serves to circulate a hydraulic medium. At least one sensor is designed and arranged to at least sense dynamic torsion of the body. At least one torsion stabilizer unit has a first end and a second end, the first end being operatively connected to the sill plate to form a first connection location and the second end being operatively connected to the supporting sheet metal to form a second connection location. The torsion stabilizer unit includes a flexible hose actuator unit having a diameter, an interior, and a length and being operatively located between the first and second connection locations. At least one control unit is designed and arranged to actively control the hose actuator unit in response to a signal of the sensor to counteract sensed torsion by controlling the volume of the hydraulic medium in the interior of the hose actuator unit. During increase of hydraulic medium in the interior of the hose actuator unit, the diameter of the hose actuator unit expands and the length of the hose actuator unit is shortened. During decrease of hydraulic medium in the interior of the hose actuator unit, the diameter of the hose actuator unit contracts and the length of said hose actuator unit is lengthened.
The novel motor vehicle includes torsion stabilizer units being designed and arranged to suppress dynamic torsion as well as static torsion of the body of the motor vehicle.
The torsion stabilizer units include hydraulic actuator units. Hydraulic actuator units are capable of attaining greater variations in length of the torsion stabilizer units compared to known piezo elements. In this way, it is possible to actively suppress the range of static torsion in the novel motor vehicle. At the same time, the typical frequency range of dynamic torsion vibrations of between approximately 10 to 20 Hz may be well handled with hydraulic actuators.
Not all hydraulic actuators have the same results when being used in the novel motor vehicle. Conventional hydraulic cylinders only effect comparatively low forces between their connection locations compared to the pressure of the used hydraulic medium and to their effective diameter. These conditions are significantly improved in the case of hydraulic hose actuator units or flexible tube actuator units. The hydraulic hose actuator units, in the case of their interior being loaded or filled, respectively, with hydraulic medium, expand with respect to their diameter andxe2x80x94at the same timexe2x80x94their length between the connecting locations is shortened. The force occurring between the connection locations multiplies by approximately five when such hose actuators are used instead of conventional hydraulic cylinders. Consequently, it is especially preferred to use hose actuators in the novel motor vehicle. Surprisingly, it has been found that the lack of compression stability and also the lack of bending stability of hydraulic hose actuators does not have a negative effect when being used in the novel motor vehicle according to the present invention. It is possible without problem to load the host actuators with hydraulic medium in the base condition of the motor vehicle such that pulling tension between the connecting locations of the hose actuator is realized. The pulling tension may then be reduced or increased to actively suppress torsion in the static region and in the dynamic region without leaving the pretension region in its first direction or in its other direction.
The hydraulic actuators in the novel motor vehicle in their mounted position may be designed and arranged to control variations in length between their connecting locationsxe2x80x94meaning the locations where the ends of the hose actuators are fixedly connected to the body of the motor vehiclexe2x80x94of a total of more than approximately 0.8 millimeters. This value is drastically more than the change in length which is attainable with known piezo elements. The change in length being attainable with known piezo elements is in a range of less than approximately {fraction (1/10)} of a millimeter. Typically, hydraulic hose actuators having a length of approximately 5 to 20 centimeters, and a diameter of some centimeters, are suitable to be applied in the novel motor vehicle. There is no problem to arrange such hose actuators in the motor vehicle.
Preferably, a hydraulic medium supply circuit, servo valves, and locking valves are associated with the hydraulic actuators. A hydraulic medium supply circuit is to be understood as a system of hydraulic medium supply conduits in which the hydraulic medium is substantially transported in circulation. For example, the hydraulic medium may be cooled, and it may also be used to cool the hydraulic actuators and the valves. The servo valves serve to subject or load the hydraulic actuators with the necessary volume of hydraulic medium. The locking valves serve to preserve certain filling conditions of the hydraulic medium in the hydraulic actuators, for example, when the motor vehicle is parked. Preserving certain filling conditions is especially important to prevent torsion of the motor vehicle being parked on a rough supporting surface and to maintain this torsion-free position by using the hydraulic actuator units.
The control unit for the torsion stabilizer units in the novel motor vehicle at least includes a sensor being designed and arranged to watch and to sense dynamic torsion of the body of the motor vehicle. The mentioned sensor or an additional sensor may be designed and arranged to also observe static torsion of the body of the motor vehicle, and to counteract the static torsion. For example, an expansion sensor being located at a transverse sheet metal of the body in front of the trunk of the motor vehicle is a sensor which is suitable to fulfill both aforementioned tasks. The location of the transverse sheet metal of the body in front of the trunk is especially suitable since such transverse sheet metal is part of most available convertibles, and it significantly indicates all torsion prevailing in the body of the convertible.
Furthermore, a bending sensor may be associated with the control unit, the bending sensor observing deflection of the body of the motor vehicle. The possible static and dynamic variations in length of the torsion stabilizers including the hydraulic actuators are great enough to counteract deflection and bending vibrations of the body in addition to torsion control. This is even the case when the novel active torsion stabilizer units of the novel motor vehicle are located at the same place as conventional passive torsion stabilizers in known convertibles.
To record interferences exciting the dynamic torsion vibrations and also the bending vibrations, acceleration sensors being arranged at the two steering stubs may be associated with the control unit. The acceleration sensors are designed and arranged to observe accelerations in a vertical direction. In this way, unevenness or roughness of the road is sensed. The acceleration sensors being located at the steering stubs may be combined with additional acceleration sensors being located at the rear axle stubs. However, it is also possible to combine the first (front) acceleration sensors with an already existing acceleration sensor of the motor vehicle. The velocity sensed by the already existing acceleration sensor of the motor vehicle allows for approximately predicting when interferences will occur at the front axle as well as at the rear axle.
Furthermore, at least one condition sensor preferably is associated with the control unit, the condition sensor being designed and arranged to sense the presently prevailing operation condition of the motor vehicle. For example, the operation condition includes the present load of the motor vehicle and the condition of the topxe2x80x94meaning whether the top is opened or closed. The operation condition of the motor vehicle has a substantial influence on how interferences have the potential of causing torsion vibrations or torsion of the body of the motor vehicle, and also on how torsion and torsion vibrations, respectively, may be effectively counteracted.
Other features and advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawing and the detailed description. It is intended that all such additional features and advantages be included herein within the scope of the present invention, as defined by the claims.